////////////////////////////////////////////////////////////////////////
//
// Copyright (C) 2011-2021 The Octave Project Developers
//
// See the file COPYRIGHT.md in the top-level directory of this
// distribution or <https://octave.org/copyright/>.
//
// This file is part of Octave.
//
// Octave is free software: you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Octave is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Octave; see the file COPYING.  If not, see
// <https://www.gnu.org/licenses/>.
//
////////////////////////////////////////////////////////////////////////

#if ! defined (octave_GenericEventNotify_h)
#define octave_GenericEventNotify_h 1

#include <QSet>

class QEvent;
class QObject;
class QWidget;

namespace octave
{

  class GenericEventNotifyReceiver;

  class GenericEventNotifySender
  {
  public:
    GenericEventNotifySender (void) : m_receivers () { }
    virtual ~GenericEventNotifySender (void) = default;

    void addReceiver (GenericEventNotifyReceiver *r)
    { m_receivers.insert (r); }

    void removeReceiver (GenericEventNotifyReceiver *r)
    { m_receivers.remove (r); }

  protected:
    bool notifyReceiversBefore (QObject *obj, QEvent *evt);
    void notifyReceiversAfter (QObject *obj, QEvent *evt);

  private:
    QSet<GenericEventNotifyReceiver*> m_receivers;
  };

  class GenericEventNotifyReceiver
  {
  public:
    GenericEventNotifyReceiver (void) { }
    virtual ~GenericEventNotifyReceiver (void) = default;

    virtual bool eventNotifyBefore (QObject *obj, QEvent *evt) = 0;
    virtual void eventNotifyAfter (QObject *obj, QEvent *evt) = 0;
  };

  inline
  bool GenericEventNotifySender::notifyReceiversBefore (QObject *obj,
      QEvent *evt)
  {
    for (auto *r : m_receivers)
      if (r->eventNotifyBefore (obj, evt))
        return true;

    return false;
  }

  inline
  void GenericEventNotifySender::notifyReceiversAfter (QObject *obj,
      QEvent *evt)
  {
    for (auto *r : m_receivers)
      r->eventNotifyAfter (obj, evt);
  }

#define DECLARE_GENERICEVENTNOTIFY_SENDER(T,B) \
class T : public B, public GenericEventNotifySender \
{ \
public: \
  T (QWidget *xparent) : B (xparent), GenericEventNotifySender () { } \
  ~ T (void) = default; \
\
  bool event (QEvent *evt) \
    { \
      bool result = true; \
      if (! notifyReceiversBefore (this, evt)) \
        result = B::event (evt); \
      notifyReceiversAfter (this, evt); \
      return result; \
    } \
}

};

#endif
